Dial switching rural telephone exchange system



Nov. 10,1931, I w. HATTON ET AL 1,831,387

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DIAL SWITCHING RURAL'IXEIILJEJI'IOIJEI EXCHANGE SYSTEM Filed March8,1930 Y 17 Sheets-Sheet 9 W HA'TTON mrmrom c;v DE VR/ENDT E. .1.ROUSSEAU ATTOXP/VE)v Nov. 10, 1931. w. HATTON ET AL 1,831,337

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DIAL SWITCHING RURAL TELEPHONE EXCHANGE SYSTEM Filed March a. 1930 1'7Sheets-Sheet 1s W. HATTON //W/YTOP5 C. DE VPIENDT E. d. POUSSEAU A TTDPNE Y Nov. 10, 1931. W. HATTON ET AL 1,331,337 I DIAL SWITCHING RURALTELEEHONE EXCHANGE SYSTEM I Fil ed March a, 1930 1'1 Sheets-Sheet 14ywHATro/v llvvf/ym s c. DEVR/ENDT I E. J ROUSSEAU ATTORNEY Nov. 10,1931. w. HATTON ET AL DIAL SWITCHING RURAL TELEPHQNE EXCHANGE SYSTEM 17Sheets-Sheet 15 Filed March 8. 1930 NNMQ W HATTUN C. DE VP/ENDT E. (J.RUUSSEAU- ATTORNEY Nov. 10, 1931. w, 0 ET L 1,831,387

DIAL SWITCHING RURAL TELEPHONE EXCHANGE SYSTEM I w HA TTON Y m mmm c. DEVP/ENDT E. .1. AOUSSEAIU wadmmr.

A Trad/var Patented Na. 10, 1931 UNITED STATES. PATENT-'- oF IcE IWILLIAM Barron-owns IDE VBIENDT, Ann ERNEs'r .TEANV ROUSSEAU, or rams,FRANCE, ASSIGNORS .ro WESTERN ELECTRIC oommmr, INCORPORATED, on NEWYORK, 1v. Y., a coaroaa'rron or NEW YORK I t DIAL swrronme RURALTELEPHONE EXCHANGE sYsrEm Application filed March 8, 1930, Seria1 No.434,214, and in Great Britain March 18, 1929.

' This invention relates to automatic telephone systems and moreparticularly to telephone exchange systems which may comprise districtoflices grouped around a center oflice, the center'ofilce in turn beingconnected to a main office. The object of the invention.

is to enable the establishment of connections in an exchange systemcomprising a number;

of small district or community oflices employing uniform directorynumbering for. all telephone lines by discriminatin as to ,thedesignation of all calls whereby t e smallest amount of equipmentcommensurate with efficient service is retained in use on any call.

The embodiment of the inventiondisclosed herein comprises \a ruralexchange System composed of one or more oflices. Connected V to the mainoflice are one or more center offices in which register translators areprovided. Connected to the center oflices directly is a number ofdistrict offices. Some of these district o'fiices may be of the tandemtype to which one'or more smaller district oflices are connected. Tielines may be provided, if desired between any'of these oflices, althoughsuch facilities will not be described herein. For all calls within theexchange system a trunk or trunks to the center oflice concerned is orare automatically taken for use and the wanted subscribers number isdialed into a register translator at the center oiflce. The uniformnumbering scheme obtains throughout theexchange system and the totalnumber group allotted to the system may be divided among the offices ona nondecimal basis. For example, a group of 20,000 subscribers lines isallotted to'the system and the individual oflices 'areflallotted groupsof 100 lines or multiples of 100 or 1000.

-' It is also desirable to providefull automatic zone meteringfacilities throughout the system and in order to make the apparatusrequired therefor as simple as possible, it is necessary to provide suchfacilities at the originating oflices in every case. If such facilitieswereprovided at an oflice other than the originating ofiice, it would benecessary provide discriminating means whereby the identity of thecalling office would be recognized. In orderto providezone meter- 1ngfacilities at each oflice, 1t 1s necessaryto include some digitdiscriminating means thereat. For this purpose register translatorcircuits which will hereinafter be called discriminating registeringdevices are associat-v ed with the trunks outgoing from all districtofiices and the register translators at the center office will alsoinclude means whereby-zone metering operations may be performed Claimsspecifically directed to the zone metering-features of the exchangesystem are belng presented in our copending application Serial No.434,216, filed concurrentvariations, one 'pair of levels ofthetranslatoris chosen inaccordance'with the setting of the first digitregister of the sender. One level of the pair is chosen by the settingof the second digit register in accordance,

with the odd or even' value of the second digit, The fifth level of thetranslator is used for setting the wipers of the translator inaccordance with thesetting of. the third digit register. The translatormay therei V fore be'set'to a particular terminal out of 200 terminalsin four of its bank levels.

These terminals are commoned in accordance with the size of'the vvariousoifices of the exchange system and the commoned terminals are jumperedto particular terminals in a marking level of a 50 point translateddigit prises levels over which the translated digits are determined anda level or levels over which switching devices may be operated forvarying the number of digits to be sent-out and the control meanstherefor.

' Referring to the drawings, Fig. 1 shows at the left a subscribersline, one of the link controlling switch. I The latter. switchcomcircuits of the communityofiice terminating atone end in a linefinder and at the other end in a plurality of parallelly connected groupselectors, tens and units 'ma rking switches for controlling thesettings of the group selectors and at the right one outgoing trunkcircuit and a subscribers' line terminating in the bank of one of thegroup selectors.

Fig. 2 shows the apparatus associated with the outgoing end of, thetrunk circuit and in the lower right portion of the figure a messageregister impulsing switch for controlling the calling line messageregister of Fig. 1 in accordance with the zone of the exchange intowhich a connection is extended.

Fig. 3 shows a discriminating registering device for registering andtranslating the first three digits dialed by a'calling subscribertogether with a trunk finder switch,

shown in the upper portion of the figure,

whereby the registering device may be as sociated with any one of agroup of trunk circuits.

Fig. 4 shows at the left the incoming end of the two-way trunk circuitshown in Fig. 2, one of the link circuits of the tandem ofiiceterminating at one end in a line finder having access to both incomingtrunk circuits and subscribers lines and at the other end in a groupfinder having access to outgoing trunks such as shown in Fig. 6 and tolocal third group finders (not shown).

Fig. 5 shows a tandem register-sender for controllin the establishmentof connections to subscri ers lines terminating in the tandem ofiiceanda link finder individual thereto for associating it with a tandemlink circuit.

Fig. 6 shows an outgoing trunk circuit and trunk circuit shown in Fig.6.

Fig. 8 shows in the left portion thereof, the incoming end of a.- trunkcircuit incoming from the tandem oflice of Fig. 4, and the line finderend of a link circuit of the center ofiice.

Figs. 9 and 10 taken together show a translator type register sender ofthe center ofiice. F g. 9 shows in the upper portion thereof a linkfinder by means of which the sender may be associated with a linkcircuit such as shown in Fig. 8 or with alinkcircuit such as shown inFig-15, in the leftportion thereof a register steering switch and in theright portion an impulse counting switch. Fig. 10 shows the digitregisters of the sender, a

'translator switch and a translated digit switch.

Fig. 11 shows a group selector of the center ofiice in which the linkcircuit of Fig. 8 terminates. v Figs. 12 and 13 takentogether showa'final selector of the center ofiice. Fig. 12 shows the apparatus ofthe final selector and Fig. 13 showing a control switch common to agroup of final selectors for controlling the setting thereof.

Fig. 14 shows a group selector or direction switch of the centero'flice.

Fig. 15 shows a subscribers line local to the center ofiice and a linkcircuit having a line finder andgroup selector means. of

.which the subscriber may establish local or outgoing connections.

Fig. 16 shows in diagrammatic form the circuits of the exchange systemillustrated in the before-mentioned figures.

' Fig. 17 shows an alternative form of impulsing circuit' whereby groupselectors may be controlled by register senders.

Fig. 18 shows schematically the association of the translator,translated digit switch,

.digit registers, impulse counting switch and digit skipping and metercontrolling relays of the'sender of Figs. 9 and 10.

Fig. 19 is a diagram showing how Figs; 1 to 15 inclusive, should be.arranged to completely disclose the invention.

Referring more particularly to Fig. 16 a part of the exchange system hasbeen schemat-.

ically illustrated as including a main oflice M, a center ofiice C,-adistrict ofiice D1 connected directly to the center oflice C, a tandemdistrict ofiice TD connected to the center office C and a districtoffice D2 subsidiary to the tandem district office TD. If a call isinitiated by a subscriber S at the district office D1, for example, aconnection is at once established over an idle link circuit DLL over theoutgoing end OJ C of an idle two-way trunk -circuit and over theincoming end BWJ 2 of such trunk circuit at the center office C. An idlelink circuit CLL at the cen .circuits outgoing therefrom to the centeroffice is automatically associated with the trunk circuit OJC taken foruse and a register sender R4 at the center oflice O is automaticallyconnected to the line finder link circuit CLL upon the seizure of thatlink. The calling .subscriber receives dial tone when both theregistering device M00 and the register sender have become associatedand then proceeds to dial the wanted subscribers number. The

discriminating digits of the telephone direc- R4 at the center oflice.The registering device MCC in addition to controlling zone metering alsodiscriminates between local and outgoing calls and if the call is foundto be local, the trunk to the center oifice C, the registering deviceMQC and the register sender R4 are all released, and the remaining twodigits dialed by the calling subscriber S are then instrumental insetting the group selector SMSl or SMS2 in which the district linkcircuit DLL terminates upon the terminal of the wanted local subscribersline, such as S1 or S2.

If the call is not to be completed locally,

however, the last two digits dialed by the calling subscriber S areregistered on registers of the sender R4 of the center office afterwhich impulses are transmitted from such sender to complete theconnection to a sub.- scribers line terminating at the center oflice',or at or through the main office M. It the Wanted subscribers lineterminates in another center oflice similar to the oiiice'C or in adistrict oflice auxiliary to such other center office, the call will berouted over the first group selector GFl, a trunk extending to the mainofiice M and the direction switch DS of the main oifice to such othercenter office. All calls initiated within the exchange system andpassing from the center oflice C to main oifice M or outgoing from theexchange system pass over the direction switch DS of the main office. Ifthe call is within the exchange system, the call-is passed through thedirection switch DS to'asecond group selector such as GF2 in the wantedcenter oflice from which the connection is further extendedby way ofa-third selector, such as GI -3 and a final selector FF in such centerofliceor over a two-way trunk to the district ofiice which is auxiliaryto such center ofiice. For calls incoming to a district oflice noregistering device, such as MCC, is connected up.

In a tandem group of offices, that is to say, a tandem district oflicetogether with the district oflices which are satellite or auxiliarythereto, all calls other than calls local to the satellite districtspass through the tandem district ofiice. Since. translation may berequired within the tandem group, it is necessary to provide a registertranslator 'for calls within the group in or .passingthrough a districtoifice. Thus, for a call originating in ,oflice D2, a subscriber S3through a link circuit, such as DLL automatically selects a trunk OJ C,BWJ 1 extending to the tandem district oflice TD. The link circuit TLLof the tandem oflice, in turn, automatically selects an idle trunk OJ C,BWJ2 extending to the center ofiice 0. Registering devices MCC both inthe district oflice D2 and in the tandem oflice link circuit TLL. Thecalling subscriber upon dialing the. discriminating digits causes theirregistration in the registering devices ofboth the district and tandemoflices and inthe register sender R4 of the center ofli:e, but theregister sender R5 of the'tandem oliiceis held idle at the time. Theregisterall seized apparatus beyond the tandem is released and theremaining digits are then registered in the tandem registersender R5Whichcontrols the setting up of the connection to'the wanted subscriber.If, however, the call was local to the district office D2 theregistering device MCC of that oflicewould have initiated. the releaseof all seized appara-. tus beyond the district office D2 and the lasttWo digits dialed by the calling subscriber S3 would then cause thegroup selector of the district office to complete the call 10- cally. Ifthe call is outgoing from a tandem group, the. register sender. R5 ofthe tandem oflice is released unused due to the discriminatingregistration set up in the registering device MGC and the tandem ofiiceT-D.

While no district offices have beendisclosed as auxiliary to the mainoffice, such oflices' ,ing device MCCof the tandem office TD dis-'crlminates as to whether the call is local within the tandem group. Ifthis is the case translator sender similar to the 4 register sender R4.

Forward impulsing is used throughout the exchange system and theswitches are all of the single motion type, but may be either powerdriven or pf the step-by-step type. Qontrol circuits are provided forthe selector switches which are of the finder type. The

control circuits may be common to a number of selector switches of thesame selecting stage and may combine the functions of a trunk finder anda marking switch.

In the system as illustrated loop dialing is employed, the loop beingformed in response to a signal sent back from the selecting stage towhich the succeeding digit impulses are to be sent. This signal is sentback over one side of the line with a ground return. I If it is desiredto eliminate the ground returnv circuit which has some disadvantages dueto difference of ground potential between the several ofiices of thesystem, an alternative arrangement of dialing and supervisory circuitsmay be employed. In this alternative arrangement shown in Fig. 17forward loop dialing is also used, the line being perman-. I

ently looped at the selecting stages byloops ment at-th'e registeringcontrol end is similar comprising high resistance. The .arrange-

